Consumption of fruits from the genus Karwinskia may cause a flaccid paralysis that can be confused with the Guillan-Barré syndrome or poliomyelitis. Paralysis resulting from consumption of such fruit has emerged as a public health problem in certain regions of Mexico. The purpose of this study was to investigate geographical factors associated with this intoxication in the 72 cases reported in Mexico from 1990 to 1994. Location of cases coincides with the distribution of the 11 reported species of Karwinskia in the country. The majority of reported cases were related to the consumption of K. humboldtiana, with a smaller number involving K. mollis, K. parvifolia, K. johnstonii, and K. rzedowskii. Most cases were located in regions with dry climates (79.2%), arid vegetation (41.7%), and altitudes under 1,000 meters above sea level (54.1%). The study establishes three different risk areas: the Balsas river region in the southwestern central part of the country; the arid northern area; and the arid and dry central area. Cases were from rural communities with low levels of schooling and poor socioeconomic conditions